Over a considerable number of years a large number of consumer products are reaching the marketplace in blow molded thermoplastic containers. Typical examples include windshield washer antifreeze and cooling system antifreeze for motor vehicles. While these are commonplace examples, the overall range of products contained in these containers is great and has been continuously increasing for a number of years. Simplicity of manufacture, durability and economy are factors which have influenced the growth in this industry.
While these blow molded containers have offered substantial advantages in many ways, there have been a number of long-felt problems for which adequate solutions have not been available. One such problem has been the difficulty in pouring from larger thermoplastic containers into receptacles having a relatively small opening. For example, in the case of the windshield washer antifreeze for motor vehicles, such products are commonly bought and transferred at motor vehicle service stations into the container provided for the purpose in the motor vehicle. Generally, funnels or the like are not readily available. As a result, there is considerable spillage with its many attendant undesirable results. In seeking a solution to this specific problem, a broader general problem in the blow molding art arose. This was the inability to blow mold an internal thread.
The present invention provides a method for blow molding an internal thread in a thermoplastic material. Such a thread has many uses, a specific example of one of which is on a pouring spout which can be attached directly to the external thread at the container opening.